You must follow Google Adsense terms of service and avoid any fraudulent  of deceptive act that google banned it below is some rules that you must not follow it, because Google strictly prohibit these types of activities.

Do not resort to fraudulent or deceptive means for generating clicks on the ads that are on your page. Some of the methods that are prohibited by Google AdSense are:

• Automated clicking programs
• Repeated manual clicks
• Using robots to generate clicks
• Clicking your own ads
• Tricking your visitors into clicking on your ads by using fraudulent means

Don’t have confusing layers of content. Content on your web page should not hide the ad text and URL. At the same time, it is advisable that you use same font type, size and color (background and font) for both the ads and the content on your web pages so that your ad does not announce itself as an outside ad. Ideally, your ad should look and feel like a part of your website.

Don’t have broken links on your site. Your website should not contain any broken links and should be easily navigable. Also, the content on your web pages should be informative, of high quality and the ads should be relevant to the content.

Don’t have old or illegal information on your site. Be careful about outdated information, plagiarized text and obscene or offensive material. Avoid using any of these on your web pages.